There are many types of pumping machines which are known in the art. These pumps vary in function from those which are used to pump fluids such as gaseous materials, through pumps for liquids, to those types of pumps which are used to pump highly viscous, particulate material. The known pumps can be used to pump other materials such as slurries, granular material, thick material sludge or the like. One particular type of pump apparatus which is well known in the art is used to pump concrete from a mixer apparatus to a remote location of utilization. These pumps are frequently hydraulically powered so as to provide a sufficient force to move the relatively heavy concrete.
Positive displacement pumps are frequently used for conveying concrete and other materials through pipelines in construction applications. An example of a positive displacement pump of this type is shown in Oakley et al., U.S. Pat. No. 5,106,272, entitled SLUDGE FLOW MEASURING SYSTEM. Positive displacement pumps offer a number of significant advantages over screw or belt conveyors in the pumping of materials such as concrete. For example, positive displacement pumps are capable of pumping thick, heavy materials which may not be practical for screw conveyors. Pump and pipeline systems also take up less space than screw or belt conveyors and, with the use of simple elbow pipes, are capable of transporting concrete around corners. Additionally, positive displacement pumps offer a reduction in noise over mechanical conveyors, as well as greater cleanliness and reduced spillage.
Many of the existing pumps use a ball valve to control the flow of concrete from the input source to the delivery line. However, in many cases, a relatively dense or coarse concrete mixture is required for various applications. With this type of concrete, it is virtually impossible to use the existing ball valve in the pump. That is, the dense and/or coarse material tends to become congested in the ball valve. This effect causes the pump to become clogged and inoperative.
The present invention relates to an apparatus for sealing the joint between two or more reciprocating pump cylinder outlets with an inlet opening on a piece of pipe oscillating between said two cylinders and in particular to such joints for reciprocating slurry pumps.
In prior art concrete pumps a pivot pipe serves to alternatively communicate with the two cylinder openings on the slurry pump as per the invention, which forms the end of the pressure pipe that supplies the dispensing nozzle. The free end of the pivot pipe is moved by a hydraulic actuator between the two openings of the cylinders in the feed and suction stroke of its pistons so that the feeding cylinder presses the slurry into the inlet of the pivot pipe, while the opening of the other cylinder is cleared, which means it is in direct communication with the supplied slurry and sucks it in. The slurry (concrete) is fed under pressure into the pivot pipe and then flows immediately from this into the pressure pipeline that is in fluid communication with a dispensing nozzle.
On positive displacement concrete pumps the upstream face of the pivot pipe that oscillates from one cylinder to another cylinder must form a fluid tight seal. The upstream face of the pivot pipe in the prior art is typically provided with a wearing ring as illustrated in the prior art, see U.S. Pat. Nos. 4,178,142 and 6,338,615. The wearing rings are necessary to limit the amount of damage and wear due to impact and abrasion caused by the relative movement between the pivot pipe 1 and openings of two cylinders on the pump.
In concrete pumping applications owners must schedule the proper maintenance and replacement of pump and pipeline components prior to a component failure during use. This prevents unnecessary and costly loss of time due to system failures, as well as the inefficient waste of concrete which may become unusable as a result of the delays associated with the failure of a pump or pipeline component. At the same time, for economic reasons, it is desirable to schedule the maintenance and replacement of pump and pipeline components only when necessary and as infrequently as possible.
In the concrete pumping business, pump maintenance is typically scheduled based upon the number of cubic yards of concrete that have been pumped. The pump owner frequently estimates the cubic yardage of concrete pumped by referring to the concrete supplier delivery tickets. In the prior art the wearing rings on the front face of the pivot pipes typically need to be replaced due to wear whenever 40,000 cumulative cubic yards of concrete has been pumped. Because conventional slurry pumps are required to withstand abrasive conditions, it is necessary that they are constructed of alloys of high hardness, thus making machining of the parts expensive and difficult. To ensure correct alignment and sealing, it is necessary that the joint elements including the wearing rings of these pumps are machined to exact requirement. This, therefore, increases the cost in the production of such pumps including the valves incorporated therewith.
In an effort to improve performance and reduce the frequency of replacement of wearing rings in the prior art (see FIG. 8), tungsten carbide tiles 51 in the shape of segmented arcs have been brazed to the forward facing surface of the wearing ring housing 53 that contacts and seals the two cylinders of the pump. Such prior art efforts have been successful in extending the frequency of necessary maintenance from 40,000 to about 75,000-80,000 cubic yards of typical concrete.
These prior art wearing rings with tungsten carbide tiles brazed thereon however frequently suffer from drawbacks at a significantly lower volume than their estimated 80,000 cubic yards of concrete. The wearing rings with tungsten carbide tiles failed prematurely before warranty. The tiles 51 on the wearing rings did not fail on account of normal operational wear. The premature failure of the wearing rings occurred due to tungsten carbide tiles being knocked off the wearing ring housing 53. The tungsten carbide tiles in the prior art illustrated in FIG. 8 where often knocked loose after the braze bonding the tiles to the wearing ring housing became weakened by the wash out of both the braze and softer material of the housing. The braze and/or softer material of the housing 53 in such prior art was washed out by the abrasiveness of the concrete flow at a much quicker rate than the tungsten carbide wore out. Prior art efforts also attempted to reduce the rate of wash out of the housing 53 by hardfacing the inner bore 55. The hardfacing assisted in slowing down tiles from being washed out, but due to the violent nature of the flow of concrete, its success was not satisfactory because it wore much quicker than the tiles, resulting in tiles having significant useful wear life still remaining being washed out prematurely. In addition to the tiles being udercut by wear at 55, material flow would penetrate the cracks 57 between adjacent tiles 51, loosening the braze thereunder and causing softer housing material to washout beneath tiles.
After one tile became knocked off, the tile adjacent the absent tile became more disposed to becoming washed out, compounding the premature failure of the wearing rings. The premature failure in prior art concrete pumps/rings would cause costly unscheduled maintenance as discussed above.
As the braze washed out at the joints between adjacent tiles on the front sealing surface of the wearing ring, concrete would leak out at those points creating pressure head losses lowering the efficiency of the pump. Whenever a first tile is knocked loose significant losses in pressure occur with the pump quickly becoming inoperable as additional tiles become knocked off. In addition, as a tile becomes displaced, the softer material behind the tile is directly exposed to material flow. The softer material wears at an accelerated rate. In the event that a tile is knocked off, if an operator fails to recognize this situation, the pivot pipe and components other than the wearing rings can quickly become damaged by the high speed oscillating pivot pipe.
There is a need in the industry for a wearing ring on a pivot pipe or similar apparatus with improved performance in durability against abrasive wear caused by concrete material flow or other abrasive materials.